EDTA and pH-sensitive crosslinking polymerization of acrylic acid, 2-acrylamidoglycolic acid, and 2-acrylamide-2-methyl-1-propanesulfonic acid



Network formation was monitored by shear storage modulus (G′) during free radical crosslinking polymerization to investigate the effects of pH and ethylenediaminetetraacetic acid (EDTA; a complex agent). Three types of acrylic monomers, acrylic acid (AAc), 2-acrylamidoglycolic acid (AmGc), and 2-acrylamido-2-methyl propanesulfonic acid (AmPS), were polymerized in the presence of a crosslinking agent. The ratio of crosslinking agent (methylene bis-acrylamide; MBAAm) to monomer was varied as: 0.583 × 10−3, 1.169 × 10−3, 1.753 × 10−3, and 2.338 × 10−3. G′ of the hydrogel in crosslinking polymerizations of AAc and AmPS was effectively increased by addition of EDTA, which was not the case for the crosslinking polymerization of AmGc. The order of magnitude of G′ differed based on the acidity of monomer. The maximum values of G′ in crosslinking polymerizations of AAc, AmGc, and AmPS were ∼20,000 Pa, 6000 Pa, and 400 Pa, respectively. G′ varied linearly with the molecular weight between crosslinks (Mwc). pH and EDTA-complex affected the rate of intramolecular propagation during crosslinking polymerization. Our results indicated that G′ was primarily affected by the following factors in the order: (1) acidity of monomer, (2) Mwc, and (3) physical interactions induced by pH and EDTA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41026.